Micrometer caliper-square



(ModeL) L. S. STARRET'T.

MIGROMETER GALIPER SQUARE.

Patented Mar. 5

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UNITED STATES IJAROY S. STARRETT, 0F

PATENT FFlGE.

ATHOL MASSA Cl-IUSETTS.

MICROMETER CAMPER-SQUARE.

SPECIFICATION formingpart of Letters Patent No. 399,167, dated March 5,1889.

Application filed February 1, 1888. Serial No. 262,624 (Model) To aZZwhom, it may concern.- 7

Be it known that I, LAROY S. S'IARRE'PI, of Athol, in the county ofll'orcesler and State of Massachusetts, have invented a new, use

j aw adjustable by a micrometcr-mit, whereby subdivisions of suchfractional parts of the unit of measure may be accurately ascertained.The instrument has also a movable binding-clasp recessed to receive themicrometer-nut, and is 'l'urnisheifl with a sprin extending from claspto jaw and surrounding the screw on wh ich the nut works. This springtakes up all backlash and limits the force with which the movable jaw ispressed by the nut against the work to be measured.

My invention consists in the described instrument as an article ofmanufacture, and in the combinations of devices set forth in theappended claims.

In the drawings, Figure 1 is a side view, on an enlarged scale, of myimproved instrument complete. Fig. 2 is a transverse section at as as,Fig. 1, made on a smaller scale. Fig. 3 is a detail in perspective.

A is the blade or beam, (shown in Fig. 1 as graduated to fortieths of aninch or other unit of measure.)

B is the fixed jaw, exlcmling from one end of the blade at a right anglethereto. Adjoining the fixed jaw B is the sliding jaw C D E, the part 0being the jaw proper, which acts with the jaw 13 as a caliper. The partD is a flat sleeve entirelysurrounding the beam, and is furnished with aset-screw, F, in the usual manner. A headed bearing-plate, G, isinterposed between the point of the screw and the edge of tho blade. Themovable jaw is formed with a grooved projecting part, E, which receivesone edge of the beam, and is beveled down to an edge along the line ofgraduations on each side thereof, thus affording an accurate reading ofthe markings and holding the jaw against an y lateral play. movable jaw,and surrounding the blade, is the usual sliding binding-clasp, K,recessed at its lower end to receive a milled nut, N, which Adjoiningthe a F engages with the threads of a screw-rod, B, projecting from themovable jaw and passing through aperforation drilled edgewise throughthe clasp. A spiral spring, S, surrounds the screw-rod R, and is heldunder compression between the jaw and clasp, thus serving to take up allbacklash between the clasp K and nut N, and also between the threads innut N and screw R, and limitin the pressure against the work to thestrength of the spring. Y I In practice thenut-X will be of slightlyless width than the recess in which it works, so that when the jaws havecome in cont act with the object to be calipcrcd a slight reversemovement of the nut-a partial revolutioni will hold the tension oi thespring without moving the jaw. I

The nut N has a cylindrical micrometer portion, M, grad ual ed intwenty-five equal divisions, the lines of subdivisions coming successivcly opposite a fixed mark on the clasp. Now, since a co mplcterotation of the nut slides the movable jaw the fortieth part of an inchin the instrument here shown, it follows that turning such nut thetwenty-fifth part of a revolution will move the j aw one twenty-fifth ofone-fortietl1-tl1at is, the thousandth part of an inch-end so on for anynumber of thousandths.

I claim as my invention 1. The described micrometer caliper-square,consisting of a graduated blade or beam, A, with a fixed jaw, B, andmovable jaw C D E, in combination with an adjustable bindingelasp, K,micrometennut M N, threaded rod R, and surrounding spring S,substantially as set forth.

2. In a measuring-instrumen t, a graduated blade, a movable jaw, and anadjustable binding-clasp on said blade, in combination with a screw-rodextending from the jaw to the clasp, a spiral spring embracing such rod,and a micrometer-nut engaging such screw, substantially as set forth.

In testimony whereof I have si good my name to this specification, inthepresence of two subscribing witnesscs, on this 26th day of January,A. l). 1888.

LAROY SJARRETT.

\Vitnessesr J AMES H. Pom), BURNSIDE E. SAwr R.

